1. Field of the Invention
The present invention relates to a tool holder which is mounted on a spindle of a machine tool to hold a tool for machining a work piece.
2. Description of Related Art
When performing machining such as cutting and grinding for a work piece, lubrication of the work piece and a working tool and cooling of heat generated by the machining are performed by sprinkling a working fluid such as oil and emulsion in a liquid state, or atomizing the liquid to spray it on a surface of the work piece to be machined from a nozzle provided toward a vicinity of a working point, in order to improve machining accuracy and increase a life of the working tool. In the case of atomizing the working fluid to spray it, there is proposed a method of mixing the working fluids of different kinds such as oil and water, and thereafter spraying the working fluids on the machined surface of the work piece, or a method of providing a plurality of nozzles to spray the working fluids of different kinds on the machined surface of the work piece from the respective nozzles.
However, since the working fluid is continuously supplied over a machining time of the work piece in order to obtain sufficient lubrication and cooling effects during the machining, there has been the problem that a large amount of working fluid is required when the working fluid is sprinkled in the liquid state. In particular, since incombustible emulsion requires to be processed as industrial waste when it is deteriorated, there has been the problem that high cost is required in processing a large amount of used or old emulsion. On the other hand, in the case of spraying the working fluid after atomizing it in order to reduce the use amount of the working fluid, there has been the problem that too much oil is scattered in the air when atomizing and spraying the oil due to the small mass of the oil, and therefore a sufficient amount of oil does not attach to the machined surface of the work piece, by which the lubrication of the work piece and the working tool and the cooling of the heat are not sufficiently performed. In addition, there has also been the problem that it is conceivable that the scattering of the atomized oil causes the risk of fire, influences human bodies and the like, in the respect of factory environment. Further, in the method of spraying the mixture solution of water and oil, or spraying those on the worked surface from the separate nozzles as described above, too much oil is also scattered in the air, and therefore, there has been the same problem.
Accordingly, in order to solve the above described problems, there has been proposed, in recent years, a method of generating a water drop with oil film by forming water supplied from an outside into a water drop and forming the oil film on a surface of the water drop as a working fluid, and machining the work piece while spraying this working fluid on the work piece (for example, see JP-A-2001-150294).